Method for producing a foundation element in the ground and foundation element

ABSTRACT

The invention relates to a method for producing a foundation element in the ground, in which a hole is produced in the ground and a hardenable mass is introduced into the hole, which hardens to form the foundation element. According to the invention provision is made in that an insert body is inserted approximately centrally into the hole, the insert body being spaced apart from a circumferential wall of the hole, wherein a ring-shaped intermediate space is formed between the circumferential wall of the hole and the insert body, and in that a hardenable mass is introduced into the ring-shaped intermediate space, which hardens to form a ring-shaped foundation element.

The invention relates to a method for producing a foundation element inthe ground, in which a hole is produced in the ground and a hardenablemass is introduced into the hole, which hardens to form the foundationelement, in accordance with the preamble of claim 1.

Furthermore, the invention relates to a foundation element in accordancewith the preamble of claim 11.

It has been long known that foundation elements are produced in theground especially for transferring greater structure loads into deeperlayers of ground. To this end, a hole is produced in the ground byremoving ground material or by displacing ground material. The hole thusproduced is filled with a hardenable mass that can harden to form thefoundation element. In doing so, the transfer of structural loads takesplace for the most part via skin friction between the outercircumferential side of the hardened foundation element and thesurrounding borehole wall and, to a small extent, via the horizontalcontact surface of the pile at the borehole bottom. To increase theload-bearing capacity of such a foundation element it is known to designthis with a corresponding axial length in order to achieve a desiredskin friction.

Furthermore, it is known that in addition to the actual load-bearingfunction of a foundation element this is also employed for geothermalpurposes. In this case, a piping system serving geothermal purposes canbe inserted into the not yet hardened mass which is filled into the holein the ground.

The invention is based on the object to provide a method and afoundation element, with which a useful purpose of a foundation elementcan be significantly widened in a particularly efficient way.

In accordance with the invention the object is achieved by a methodhaving the features of claim 1 and by a foundation element having thefeatures of claim 11. Preferred embodiments of the invention are statedin the respective dependent claims.

The method according to the invention is characterized in that an insertbody is inserted approximately centrally into the hole, the insert bodybeing spaced apart from a circumferential wall of the hole, wherein aring-shaped intermediate space is formed between the circumferentialwall of the hole and the insert body, and in that the hardenable mass isintroduced into the ring-shaped intermediate space, which hardens toform a ring-shaped foundation element.

A basic idea of the invention can be seen in the fact that a foundationelement in the ground is no longer of solid construction over the entirefoundation cross-section but designed as a ring-shaped foundationelement. This is achieved in that a preferably releasable insert body isprovided approximately centrally, wherein the hardenable mass ispreferably introduced exclusively into the ring-shaped intermediatespace between a wall of the hole in the ground and the outer side of theinsert body towards the foundation element and hardens therein.

Though, it is a finding of the invention that a ring-shaped design hasno significant influence on a load-bearing function of the foundationelement because, as with a solid body foundation element, the same skinfriction continues to be present on the outer circumferential side whichis of particular relevance for the load-bearing capacity. It is only inthe region of the contact surface that the ring shape can result in acertain reduction of the contact surface. By providing a centralnon-load-bearing region on the contact surface of the foundation elementthe load-bearing capacity is therefore only lowered to a marginalextent, yet at the same time the required hardenable mass is reducedconsiderably. This is cost-saving.

Moreover, a space inside the ring-shaped foundation element can be usedin a variety of ways, for instance for geothermal purposes, formeasurement purposes or for numerous other functions.

A preferred embodiment of the invention resides in the fact that theinsert body is of tubular design. The insert body can substantially onlyserve for the support and design of the inner ring contour of thering-shaped foundation element. The insert body can remain in thefoundation element or be released therefrom. The insert body can consistof a metal, especially steel, or a plastic material of lowerload-bearing capacity.

According to a further development of the invention, on intendedrecovery of the insert body it is advantageous that the insert body issurrounded on its outer side by a sheathing element and that afterhardening of the mass to the ring-shaped foundation element the insertbody is withdrawn from the foundation element, wherein the sheathingelement remains on the ring-shaped foundation element. Thereby thesheathing element can be a thin tube or preferably a film, a fabric oranother type of dimensionally instable planar formation. The sheathingelement is fixed as a lost element on the outer side of the insert body.The sheathing element can remain on the hardened foundation elementwhile the insert body can be easily withdrawn from the sheathing elementand be reused. This also results in a further saving of material andcosts.

To increase the load-bearing capacity of the ring-shaped foundationelement consisting of the hardenable mass it is expedient according to amethod variant of the invention that prior to the hardening of the massone or several reinforcement elements can be inserted into thering-shaped intermediate space. The reinforcement elements can inparticular be bars, girders or cages of steel.

According to a further development of the invention it is advantageousthat the ring-shaped foundation element is designed to absorb a desiredfoundation load, in particular a cross-sectional surface of thering-shaped foundation element can be designed such that the necessaryaxial forces can be absorbed and transferred via the outercircumferential surface. In addition, the foundation element can bedesigned with a base plate so that contact forces can also betransmitted directly via this base plate of the foundation element thatis otherwise designed with a cavity.

Basically, the insert body can be designed in one piece. Especially forgreater depths and thus for foundation elements of greater length it maybe expedient in accordance with a further development that the insertbody is constructed of ring-shaped segments. The ring-shaped segmentscan be connected axially to each other so that a longer insert body isformed. The insert body can have the same diameter over its length orshow a certain conicity, with the diameter enlarging in the upwarddirection. This facilitates withdrawal of the insert body from thefoundation element.

According to an advantageous embodiment of the invention provision ismade in that a central cavity is surrounded by the ring-shapedfoundation element. The central cavity can be used for various purposes,for example for the insertion of a heat exchanger element for geothermalpurposes. In this case, heat can be extracted from the ground by meansof a heat pump and used for heating purposes, in particular in thestructure which is erected on the foundation element. Alternatively, forcooling purposes heat can also be dissipated into the ground, whereby,for example, a climatization and cooling can be realized in thestructure. However, the cavity can also be deployed for metrologicalpurposes as well as for inspection.

According to a further development of the invention it is especiallyadvantageous that during the production of the hole ground material isremoved and conveyed as excavated material out of the hole and that atleast a part of the excavated material is returned into the centralcavity of the ring-shaped foundation element. This is advantageous intwo respects: On the one hand, excavated material can thus be returnedinto the ground so that the excavated material does not have to betransported away from the construction site and deposited. As a result,transportation and landfill costs can be saved. On the other hand, thefoundation element is additionally reinforced by the filled-up centralcavity so that the strength of the foundation element and therefore alsoits load-bearing capacity are enhanced.

Basically, the hole for forming the foundation element can be producedin any chosen way. According to an embodiment variant of the inventionit is especially advantageous that the hole is produced through drillingwith a circular cross-section or through cutting with an angularcross-section. In the case of drilling, both material-removing drillingand displacement drilling can be employed. In displacement drilling theground material from the region of the hole is displaced into thesurrounding ground by means of a displacement drill.

An angular cross-section can in particular be achieved by a diaphragmwall cutter, with which a diaphragm wall segment having a preferablyrectangular cross section is produced.

Within the meaning of the invention a foundation element in the groundis to be understood in a broad sense, in which case not only can this beused for absorbing structural loads but also for forming a cut-off wallby adjoining foundation elements for example.

Another preferred method variant of the invention resides in the factthat the ground material is mixed with a concrete mass. In this way,so-called ground mortar can be produced which can be introduced into theground as the hardenable mass in order to form the ring-shapedfoundation element. However, the ring-shaped foundation element can alsobe produced from a concrete mass or a ground mortar of higher strength,while a ground mortar of lower strength is introduced into the centralcavity. In this way, a saving in excavated material can be realizedwhilst still ensuring relatively high strength and load-bearing capacityof the foundation element.

The invention further comprises a foundation element which ischaracterized in that this is produced in a ring-shaped manner from ahardenable mass in the ground. Hence, the foundation element is not overthe entire cross-section of the foundation element but only in aring-shaped region produced of the hardenable mass. The foundationelement is in particular produced using the previously described methodaccording to the invention. The advantages set out beforehand can beachieved by way of the foundation element according to the invention.

According to a further development of the invention it is especiallyadvantageous that a central cavity is designed in the ring-shapedfoundation element. This can be used to accommodate different functionalcomponents, such as heat exchanger elements or measuring instruments.

According to a further embodiment variant of the invention it isespecially advantageous that the central cavity in the ring-shapedfoundation element is filled with a non-hardenable material, inparticular removed ground material. As a result, transportation andlandfill costs can be saved.

The invention is described further by way of a preferred, exemplaryembodiment illustrated schematically in the accompanying drawings,wherein show:

FIG. 1 a cross-sectional view during the production of a foundationelement according to the invention with inserted insert body; and

FIG. 2 a cross-sectional view of the foundation element of FIG. 1 afterremoval of the insert body.

To produce a foundation element 10 according to the invention in aground 5 a hole 7 is initially introduced into the ground 5. Theproduction of the hole 7 can take place in a conventional way e.g.through drilling or cutting. The drilling concerned can be cased oruncased drilling.

Before introduction of a hardenable mass into the hole 7 an insert body20 is inserted into a central region of the hole 7. The insert body 20can be inserted as early as during the sinking of the hole 7 or only oncompletion of the hole 7. In the illustrated embodiment the insert body20 is constructed of three ring-shaped segments 22 in total which areaxially connected to each other.

The insert body 20 is inserted approximately centrally into the hole 7such that a defined distance is formed between an outer side of theinsert body 20 and a circumferential wall 8 of the hole 7. In this way,an intermediate space is created which is filled with a hardenable massto form the ring-shaped foundation element 10.

In the illustrated embodiment the insert body 20 is placed onto a bottom14 of the hole 7. On its outer side the insert body 20 has a sheathingbody 24 that can be a film or a fabric for example. The sheathing body24 can be a lost element which mainly serves to prevent direct adhesionof the hardenable mass to the insert body 20. The sheathing body 24 canbe open or closed at its lower end.

After hardening of the hardenable mass to form the ring-shapedfoundation element 10 the insert body 20 is pulled upwards out of thehole 7 so that a central cavity 12 is formed in the ring-shapedfoundation element 10, as illustrated graphically in FIG. 2. Thesheathing body 24 remains on the inner side of the ring-shapedfoundation element 10 and can, for example, serve to additionally sealthe central cavity 12 with respect to the ring-shaped foundation element10.

According to an embodiment of the invention a material of the groundthat arises as excavation material 30 during the production of the hole7 can be introduced into the central cavity 12. This reduces the amountof excavated material 30 that has to be transported away from theconstruction site and deposited. At the same time, in the illustratedembodiment the excavated material 30 serves for the stabilization andinner support of the ring-shaped foundation element 10. The ability ofthe latter to transfer structural loads into the ground 5 isaccomplished to a decisive degree through the skin friction of the outerside of the foundation element 10 with the circumferential wall 8 of thehole 7.

1.-13. (canceled)
 14. The method for producing a foundation element inthe ground, in which a hole is produced in the ground and a hardenablemass is introduced into the hole, which hardens to the foundationelement, wherein an insert body is inserted approximately centrally intothe hole, the insert body being spaced apart from a circumferential wallof the hole, wherein a ring-shaped intermediate space is formed betweenthe circumferential wall of the hole and the insert body, and whereinthe hardenable mass is introduced into the ring-shaped intermediatespace, which hardens to form a ring-shaped foundation element, whereinthe insert body is surrounded on its outer side by a sheathing elementand after hardening of the mass to the ring-shaped foundation elementthe insert body is withdrawn from the foundation element, wherein thesheathing element remains on the ring-shaped foundation element.
 15. Amethod according to claim 14, wherein the insert body is of tubulardesign.
 16. A method according to claim 14, wherein prior to thehardening of the mass one or several reinforcement elements are insertedinto the ring-shaped intermediate space.
 17. A method according to claim14, wherein the ring-shaped foundation element is designed to absorb adesired foundation load.
 18. A method according to claim 14, wherein theinsert body is constructed of ring-shaped segments.
 19. A methodaccording to claim 14, wherein a central cavity is surrounded by thering-shaped foundation element.
 20. A method according to claim 19,wherein during the production of the hole ground material is removed andconveyed as excavated material out of the hole and at least a part ofthe excavated material is returned into the central cavity of thering-shaped foundation element.
 21. A method according to claim 14,wherein the hole is produced through drilling with a circularcross-section or through cutting with an angular cross-section.
 22. Amethod according to claim 20, wherein the ground material is mixed witha concrete mass.
 23. The foundation element produced pursuant to amethod according to claim 14, wherein the foundation element is producedin a ring-shaped manner from a hardenable mass in the ground, whereinthe sheathing element remains on the ring-shaped foundation element. 24.A foundation element according to claim 23, wherein a central cavity isdesigned in the ring-shaped foundation element.
 25. A foundation elementaccording to claim 24, wherein the central cavity in the ring-shapedfoundation element is filled with a non-hardenable material, inparticular removed ground material.